Taste stimuli encountered in the real world like tap water, foods, and beverages are mixtures. The major objective of this study is to provide a framework that will permit the prediction of the taste of a mixture from knowledge of the tastes of its components and the manner in which it was tasted. When taste substances are mixed, their tastes change in intensity even when there are no chemical interactions among the tastants. The mixture interactions depend in part on the shapes of the psychophysical functions that describe perceived intensity versus concentration and in part on other variables not yet identified. The taste of a complex solution actually comes from two sources: the solutes and the water solvent in which they are dissolved. The taste of water itself depends on the substance to which the tongue is adapted. Water can taste sweet, sour, salty, or bitter if it follows adaptation to appropriate substances. For example, adaptation of NaCl makes water taste bitter-sour. Under normal conditons, the tongue is adapted to saliva which contains NaCl. The water taste produced by adaptation to saliva contributes to the tastes of mixtures. We propose to study the tastes of complex solutions by 1) identifying the variables that control mixture interactions and 2) determining the contribution of water taste to the tastes of complex solutions. The experiments will be conducted on human subjects with the ratio scaling technique of magnitude estimation, with matching procedures, and with threshold procedures. The results of these studies may suggest ways to improve the tastes of important mixtures like tap water since rules of mixture interactions could be used to predict how the removal or addition of a particular substance would change the taste of the mixture.